In the quest for hard surface cleaners which have efficacy against a variety of soils and stains, various heavy duty cleansers have been developed. As an example, U.S. Pat. No. 3,985,668 issued to Hartman, shows a combination of perlite (an expanded silica abrasive, which is here used as a filler), a colloid-forming clay, in combination with a hypochlorite bleach, a surfactant and a buffer in which abrasives are suspended. A clay thickened system of this type tends to set up or harden upon storage due to the false body nature of the thickeners. They require shaking before use to break down the false body structure. Further prior art cleaners which attempt to suspend abrasives use either inorganic colloid thickeners only or mixed surfactant thickeners at high levels of surfactants. Additionally, syneresis becomes a problem as the solids portion of such cleansers substantially separate from the liquids portion. One way to alleviate this is to use a perlite type material with specified particle size as defined in U.S. Pat. No. 3,985,668, issued to Hartman. Additionally, high levels of surfactants can be used to form a plastic rheology for suspension of abrasives. However, they also have a detrimental effect on hypochlorite stability. These mixed surfactant thickened compositions, for example, U.S. Pat. No. 4,352,678, issued to Jones et al, have been used to suspend abrasives and incorporate a source of hypochlorite bleach. However, this particular reference must incorporate large amounts of surfactants in order to suspend abrasives. This has the unfortunate disadvantage of resultant poor hypochlorite stability in terms of half-life stability at 50.degree. C. for low levels of hypochlorite (0.5% sodium hypochlorite initial level). For the instant purpose, half-life stability is defined as the amount of time it takes for 50% of the initial amount of bleach present in a given composition to decompose.
Other efforts in the cleanser field have included: U.S. Pat. No. 4,337,163, issued to Schilp, which related to a bleach thickened with a combination of amine oxides and anionic surfactants. Abrasives are unable to be suspended in the Schlip formulas. U.S. Pat. No. 4,287,079, issued to Robinson, on the other hand, related to a clay/silicon dioxide thickened, bleach-containing abrasive cleanser which could contain an anionic surfactant. Due to the clay-thickened rheology, cleansers of this sort quickly dry out and set up. While these type of cleansers thus become less flowable over time, they are unfortunately also plagued by significant syneresis problems. U.S. Pat. No. 3,956,158, (also British Pat. No. 1,418,671) issued to Donaldson shows an abrasive-containing bleach thickened with insoluble detergent filaments. As described in U.S. Pat. No. 4,352,678, compositions such as those disclosed in U.S. Pat. No. 3,956,158 have numerous disadvantages, including low detergency and lack of physical and chemical stability at higher temperatures. Lastly, U.S. Pat. No. 3,558,496, issued to Zmoda, shows a hypochlorite bleach thickened with negatively and positively charged clays. Negatively charged clays include smectites, montomorillonites, etc., which are common clays. The positively charged clays was a fibrillar aluminum oxide. The reference does not mention whether abrasives may be suspended by such a thickened bleach. Again, due to presence of the former clays, a false body rheology is likely to occur in which hardening soon occurs and probable increased syneresis is observed.
There therefore remains a need for a thickened hard surface cleanser which is capable of suspending abrasives, exhibits no syneresis over time, does not require shaking before use and has long-term bleach stability.